JSON is [faster and more compact][1], so it is easier on the server, and [easier to parse][2] in most application languages -- while still being human-readable. 

Since the API is [returning data, rather than markup, JSON is a much better choice than XML][3].

If you insist on XML, there are a [great][4]   [many][5]   [ways][6]   [to convert][7] the data yourself, without loading the API servers with extra XML baggage.


  [1]: http://stackoverflow.com/a/4596514/331508
  [2]: http://stackoverflow.com/a/1743573/331508
  [3]: http://stackoverflow.com/a/329683/331508
  [4]: http://stackoverflow.com/q/1773550/331508
  [5]: http://stackoverflow.com/q/856833/331508
  [6]: http://stackoverflow.com/q/559296/331508
  [7]: http://stackoverflow.com/q/814001/331508